Information technology enhances the nature of mathematics as an empirical discipline, leading to an approach called "experimental mathematics" (EM). It fosters the use of technology-based interactive resources (IRs) in mathematics education, giving mathematics an experimental dimension and reflecting a tension between the empirical-inductive nature of IRs and formal mathematics (FM). Our qualitative research focused on professional development (PD) for IR-based teaching of EM intertwined with FM based on a threefold theoretical framework that combines the mathematical knowledge required by EM, the pedagogical functionality of IRs, and instrumental orchestration. The research analyzed 14 high school teachers' documents generated in the course of a PD program, revealing the evolution of their orientation. We argue that teachers' evolving orientation toward IR-based EM inclusion in school mathematics is the result of meticulous dynamic PD design implementing three key aspects framed by the threefold theoretical framework: teachers playing various roles during the PD, teacher-researcher collaboration, and theoretical support. The beginning of the evolution of the teachers' orientation toward IR-based EM inclusion in school mathematics was made possible by a design grounded in the above theoretical framework and observed through its lens.